AAA is urging the U.S. Department of Transportation to block a plan to increase tolls by as much as 50 percent on the bridges and tunnels between New York City and New Jersey beginning Sunday, saying the hikes violate federal law.

Besides the sticker shock to commuters, the motorists group said Thursday that it objects to using toll revenues for building the new World Trade Center at the site owned by the Port Authority of New York and New Jersey.

“One of our primary missions is to make sure that any tolls and revenue and any user fees go back into transportation,” said Marta Genovese, vice president of legal affairs for AAA. “But in this case it’s going into a speculative office development.”

The group said the increase violates a federal law that requires bridge tolls to be “just and reasonable,” and it sent a letter to Transportation Secretary Ray LaHood asking him to act.

“It’s an egregious example of the motorists getting ripped off,” AAA New York spokesman Robert Sinclair said.

Cash tolls on the George Washington Bridge, Holland Tunnel, Lincoln Tunnel, Goethals Bridge, Bayonne Bride and Outerbridge Crossing are scheduled to rise from $8 to $12 at 3 a.m. on Sunday. Peak-hour tolls for users of the E-ZPass electronic payment system will go from $8 to $9.50.

By December 2015 cash tolls would increase gradually to $15 under a plan approved Aug. 19 by the Port Authority of New York and New Jersey. Peak-hour tolls for E-ZPass users would rise gradually to $12.50.

In addition to the bridge toll increases, the fare on the Port Authority Trans-Hudson subway line will rise from $1.75 to $2 on Sunday. By 2015 it is scheduled to increase to $2.75.

The AAA claims the increases violate a 1987 U.S. law regulating bridge tolls. The law applies to bridges that carry interstate commerce over “any of the navigable waters of the United States.”

The Department of Transportation said LaHood would respond directly to the AAA. It gave no immediate comment.

The Associated Press left a message for a port authority representative. Its board members have said the fare increases will pay for construction that is fueling the region’s economy.

It also says it needs more money to replace the cables on the George Washington Bridge, rehabilitate the corkscrew-shaped ramp into the Lincoln Tunnel and take on other maintenance projects. The authority receives no tax money and supports itself through tolls, fares, fees and rent paid by businesses at its ports, airports and other properties.

The AAA said it may also sue the authority to try to block the increase.

Genovese said the group has not asked a court for a temporary restraining order because it is still trying to obtain a revised capital spending plan from the agency.